Fluid-fuel burners

ABSTRACT

A fluid-fuel burner having an annular injection system wherein the oxidant is caused to undergo a forced rotation and the fuel is fed to the center of the injected oxidant. The injection system is positioned at the entrance of a tunnel which is initially divergent and thereafter cylindrical over a length between 0.5 and 1 times the tunnel diameter. The cylindrical portion being followed by a passage of evolutive section at least one-half of which has walls converging up to an outlet formed by a pseudo-rectangular slit at least one of the smaller sides of which is joined to the corresponding tunnel surface by a convex rounded portion.

United States Patent [1 1 Kissel 1 FLUID-FUEL BURNERS Roland Roger Kissel, Le Vesinet, France [75] Inventor:

[73] Assignee: Societe Anonyme Heurtey, Paris,

France [22] Filed: Dec. 2, 1971 [21] Appl. N0.: 203,955 [30] Foreign Application Priority Data Dec. 16, 1970 France 7045328 [52] U.S. Cl 431/158, 431/182, 431/353 [51] Int. Cl. F23r 1/00 [58] Field of Search 431/158, 182, 183, 431/353 [56] References Cited UNITED STATES PATENTS 3,612,737 10/1971 Sharan 431/183 3,671,172 6/1972 Chedaille et al 431/182 FOREIGN PATENTS 0R APPLICATIONS 901,222 10/1944 France 431/158 Primary ExaminerCarroll B. Dority, Jr. Attorney.lohn .I. McGlew et a1.

[57] ABSTRACT A fluid-fuel burner having an annular injection system wherein the oxidant is caused to undergo a forced rotation and the fuel is fed to thecenter-of the injected oxidant. The injection system is positioned at the entrance of a tunnel which is initially divergent and thereafter cylindrical over a length between 0.5 and 1 times the tunnel diameter. The cylindrical portion being followed by a passage of evolutive section at least one-half of which has walls converging up to an outlet formed by a pseudo-rectangular slit at least one of the smaller sides of which is joined to the corresponding tunnel surface by a convex rounded portion.

3 Claims, 4 Drawing Figures PATENTEDSEPHW 3.758.263

sum; or 2 :[NVENToR ROLAND ROGER mesa HTTORNEY FLUID-FUEL BURNERS The technical province of this invention is that of burners.

In order to achieve heating through the agency of a wall or an arch, so-called flat-flame burners have been used heretofore.

In such burners the flame develops radially along the divergent tunnel through the burner, in a plane at right angles to the axis thereof.

The disadvantage of such a system resides in the fact that the developed flame is not invariably flat at different combustion rates. At slow rates, the flame may separate from the wall and become spheroidal, and when the surface of the product to be heated lies near a burner outlet, the product may be overheated at that particular place.

The present invention has principally for its object to overcome this danger and ensure satisfactory operation at all heat output rates.

The invention accordingly relates to a fluid-fuel burner, characterized by the fact that it comprises an.

annular air injection system whereby to cause the oxidant to undergo a forced rotation, which gyratorily injected air has the fuel fed into it from the centre through metering and distributing orifices which allow achieving a mixture adequate to ensure rapid combustion, said injection system beng positioned at the entrance to a tunnel which is initially divergent and thereafter cylindrical over a length included between 0.5 and 1 times the diameter of the tunnel, said cylindrical portion being followed by a passage of changing shape, at least one-half of which has convergent walls leading to an outlet formed by a pseudo-rectangular slit the smaller side of which reaches up to the tunnel surface extension through the medium of a rounded convex portion.

It is thereby possible to obtain a flame that spreads out in a thin-walled volume adjacent the plane passing through the burner axis and the major axis of the rectangular bumer outlet.

The field of application of a burner according to this invention is that of direct wall heating, the flat flame flattening itself against the wall over a large contact area, thereby to develop uniform high temperatures.

The description which follows with reference to the accompanying non-limitative exemplary drawings will give a clear understanding of how the invention can be carried into practice.

In the drawings,

FIG. 1 shows a burner according to the invention in axial section with a partial central cutaway;

FIGS. 2 and 3 are sections taken through the lines Illl and IIIIII respectively of FIG. 1; and

FIG. 4 is a front view of said burner.

In the exemplary embodiment herein described, the burner comprises a central tube 1 for housing a pilot burner therein (not shown), surrounded by a gas delivery tube 2, whereby the gas flows through the annular clearance between the tubes 1 and 2.

The tube 2 accordingly comprises a connection point 3 ahead of a flange 4 adapted to be secured to a supporting plate 5 fitted over a gasket and bolted to the face 6 of a furnace.

Tube 2 passes through a sleeve 7 fast with flange 5 and is surrounded by a ring 8 which is made of refractory material and is in turn surrounded by the end of a liner 9. The liner 9 is surrounded by a refractory ring l0 enclosed in an outer jacket 11. Sleeve 7, liner 9 and jacket 11 have their end sections welded against flange 5.

Liner 9 is secured by worm screws 12 over the stub of an air distributor 13 formed with a circle of calibrated holes 14 uniformly spaced from the burner axis and fonning an angle to the direction thereof. The central bore 15 of distributor 13 has extending therethrough a stub 16 screwed to tube 2. Similarly, stub surrounds a hollow nosepiece 17 screwed to tube I, which tube comprises spacers l8 proximate the junction for locating said tube within tube 2. Nosepiece 17 spigots into stub 16 with slight clearance through the agency of a reinforced head which, in the rear wall of this hollow reinforcement, embodies nozzles 19 which converge slightly towards the internal annular chamber 20 of said head.

From chamber 20 debouch, into the front face, fuelsupply axial nozzles 21 and radial nozzles 21a, which nozzles 21a have port adjacent the end section of stub 16.

Stub l6 and nosepiece l7 protrude slightly forward of the rear face of distributor 13, into a tunnel 22.

The outer region of the distributor accordingly com prises, in addition to a seal 23 applied against the wall 24 of the burner housing, into the thickness of the furnace wall, a ring of studs 25 for restraining a surrounding shell 26 provided internally with means 27 for fastening into a moulded refractory lining 28 forming a flame guiding and shaping tunnel. At the perimeter of the nose, this tunnel includes a cylindrical portion 29 followed by a frusto-conical section 32 which is joined to the entry of cylindrical section 31 having a length included between 0.5 and I times the diameter of the divergent outlet.

Cylindrical section 31 is succeeded by an evolutive convergent section 32, one-half of which is formed with parallel edges that are extensions of the generatrixed of cylindrical section 31, and the other half of which is a convergent section, whereby to ultimately extend up to an elongated rectangular outlet 33. In the example shown in the drawings, the non-convergent section is extended in a straight line along the contour 34 up to the outlet through the rectangular slit 33 in the front face 35 of the tunnel, whereas the opposite edge is faced by a rounded divergent section 36.

This is becuase of the fact that the burner is designed to operate at a level close to that of a hearth, and it is therefore required to cause an upward development of the flat flame which it produces.

Obviously, were the burner designed to operate at a sufficient distance from the bottom of a chamber, the two smaller edges of the rectangular slit could be formed with symmetrical or asymmetrical rounded portions 36.

Operation of the system hereinbefore described is based on admission of gas through the connection 3 and admission of air through the conduit 24a which leads the air to the periphery of liner 9 through the wall of the heated chamber. The air enters this liner surrounding tube 2 through a series of holes suitably arranged in adjacent rings 9a and 9b, ahead of refractory supports 8 and 10. An igniter 37 sealingly extends through flange 4, flange 5 and distributor 13, along the length of tube 2, in such manner that its active igniting elements be positioned adjacent the fuel delivery nozzles of nosepiece l7.

Responsively to the rotation imparted to the air flow by the inclined holes 14 at the periphery of the gas jets flowing axially from nozzles 21 and radially from nozzles 21a, a gyrating motion of the burning mixture is obtained through divergent section 30 followed by cylindrical tunnel 31.

The gyration of the gases is preserved by the rounded shape of the lips on exit from the rectangular outlet.

If a burner as above described is so positioned that the plane passing through the burner axis and the major axis of the recantgular outlet lies close to a wall to be heated, the recirculation phenomena at the centre of the flame improve the Coanda effect and the flame flattens against the wall and in so doing generates an ovalshaped heating zone of large size at high temperature.

A burner of this kind is particularly well-suited for heating a furnace wall at any regime, for converting the same into a radiant wall to permit direct heating of products placed in the furnace, and even for the external heating of a gastight bell wall beneath which the products to be treated are placed in a recirculating atmosphere gas, whereby the wall facing the bell is protected against the hot spot" effects which ordinary burners inflict upon it.

It goes without saying that changes and substitutions may be made in he embodiment hereinbefore described without departing from the scope of the invention. By way of example, the evolutive passage of the convergent section 32 could be shaped for convergent evolution in two mutually perpendicular directions instead of having parallel edges along one-half of its length, that is to say that said parallel edges could be caused to move towards each other along any convenient profile.

What l claim is:

l. A fluid-fuel burner, characterized by the fact that it comprises an annular air injection system which imparts a forced rotation to the oxidant and within which is disposed a member for delivering fuel so metered and distributed as to ensure rapid combustion, said injection system being positioned at the inlet to a tunnel consisting of a divergent section followed by a cylindrical section of length included between 0.5 and 1 times the tunnel diameter, said cylindrical portion being in turn followed by a passage of evolutive section at least one-half of which has walls converging up to an outlet formed by a pseudo-rectangular slit at least one of the smaller sides of which is joined to the corresponding tunnel surface by a convex rounded portion.

2. A burner according to claim 1, characterized by the fact that it comprises an air distributor having a thick wall embodying a ring of holes which are equidistant from the burner axis but run at an angle to the direction thereof;

3. A burner according to calim 1, characterized by the fact that said fuel supply member is formed by a centrally positioned distribution nose provided with end longitudinally disposed nozzles and divergent radial nozzles. 

1. A fluid-fuel burner, characterized by the fact that it comprises an annular air injection system which imparts a forced rotation to the oxidant and within which is disposed a member for delivering fuel so metered and distributed as to ensure rapid combustion, said injection system being positioned at the inlet to a tunnel consisting of a divergent section followed by a cylindrical section of length included between 0.5 and 1 times the tunnel diameter, said cylindrical portion being in turn followed by a passage of evolutive section at least one-half of which has walls converging up to an outlet formed by a pseudorectangular slit at least one of the smaller sides of which is joined to the corresponding tunnel surface by a convex rounded portion.
 2. A burner according to claim 1, characterized by the fact that it comprises an air distributor having a thick wall embodying a ring of holes which are equidistant from the burner axis but run at an angle to the direction thereof.
 3. A burner according to claim 1, characterized by the fact that said fuel supply member is formed by a centrally positioned distribution nose provided with end longitudinally disposed nozzles and divergent radial nozzles. 